Abstract:

A plurality of assembly sheets are placed on an upper surface of a
substrate adsorption platform, and a pressing plate is placed on the
plurality of assembly sheets placed on the substrate adsorption platform
such that the plurality of assembly sheets are pressed by the pressing
plate. In this state, a DC power supply device is turned on and causes
the upper surface of the substrate adsorption platform to be charged,
thereby causing the plurality of assembly sheets to be adsorbed on the
upper surface by an electrostatic force. Then, the pressing plate placed
on the plurality of assembly sheets is removed while the upper surface of
the substrate adsorption platform is charged, and automatic appearance
inspection is performed on the plurality of assembly sheets adsorbed on
the upper surface of the substrate adsorption platform.

Claims:

1. A method of inspecting a printed circuit board comprising the steps
of: placing said printed circuit board on a support surface of an
adsorption platform; placing a pressing member on said printed circuit
board placed on said support surface such that said printed circuit board
is pressed by an insulating pressing surface of said pressing member;
adsorbing said printed circuit board on said support surface by an
electrostatic force by charging said support surface while said printed
circuit board and said pressing member are placed on said support
surface; removing said pressing member placed on said printed circuit
board while said support surface is charged; and performing automatic
appearance inspection on said printed circuit board adsorbed on said
support surface.

2. The method of inspecting the printed circuit board according to claim
1, wherein said pressing surface of said pressing member is formed of
insulating glass or insulating resin.

3. The method of inspecting the printed circuit board according to claim
2, wherein said resin includes at least one of polyvinyl chloride,
acrylic resin, polycarbonate and polytetrafluoroethylene.

4. The method of inspecting the printed circuit board according to claim
1, wherein said pressing member is formed of a material having light
transmission properties.

5. A method of manufacturing a printed circuit board, comprising the
steps of: preparing the printed circuit board before inspection by
forming a conductor trace on an insulating layer; placing said printed
circuit board before inspection on a support surface of an adsorption
platform; placing a pressing member on said printed circuit board before
inspection placed on said support surface such that said printed circuit
board before inspection is pressed by an insulating pressing surface of
said pressing member; adsorbing said printed circuit board before
inspection on said support surface by an electrostatic force by charging
said support surface while said printed circuit board before inspection
and said pressing member are placed on said support surface; removing
said pressing member placed on said printed circuit board before
inspection while said support surface is charged; and performing
automatic appearance inspection on said printed circuit board before
inspection adsorbed on said support surface.

6. An inspection device of a printed circuit board comprising: an
adsorption platform that has a support surface on which the printed
circuit board is placed, and is configured such that said support surface
can be switched between a charged state and an uncharged state; a
pressing member that has an insulating pressing surface; a moving device
arranged to move said pressing member; a detection device arranged to
perform automatic appearance inspection on said printed circuit board
placed on said support surface of said adsorption platform; and a
controller arranged to control operations of said adsorption platform,
said moving device and said detection device, wherein said controller:
controls said moving device to place said pressing member on said printed
circuit board such that said printed circuit board is pressed by said
pressing surface while said printed circuit board is placed on said
support surface of said adsorption platform; switches said support
surface of said adsorption platform to the charged state while said
printed circuit board and said pressing member are placed on said support
surface to cause said printed circuit board to be adsorbed on said
support surface by an electrostatic force; controls said moving device to
remove said pressing member placed on said printed circuit board in said
charged state of said support surface; and controls said detection device
to perform automatic appearance inspection on said printed circuit board
adsorbed on said support surface.

Description:

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a method of inspecting a printed
circuit board, a method of manufacturing a printed circuit board and an
inspection device of a printed circuit board.

[0003] 2. Description of the Background Art

[0004] Electronic apparatuses such as hard disk drives or cellular
telephones are provided with printed circuit boards having conductor
traces formed thereon. Sometimes, automatic appearance inspection such as
AVI (Automatic Visual Inspection) is performed in manufacture of such
printed circuit boards.

[0005] In the AVI, the presence/absence of defective pieces having defects
in conductor traces, dimensional errors of conductor traces, defects in
terminals and damaged resist surfaces and so on can be determined in a
short period of time in the final stage of manufacturing steps of the
printed circuit boards.

[0006] The AVI is performed in the following manner, for example. First, a
good printed circuit board with no defect is imaged by an imaging device,
and obtained image data is stored in a memory as master data. Then, a
printed circuit board to be inspected is imaged by the imaging device,
and obtained image data is stored in the memory as inspection target
data. The master data and the inspection target data are subsequently
compared with each other, so that determination as to whether or not the
printed circuit board is defective is made.

[0007] In the AVI, since the determination as to whether or not the
printed circuit board is defective is made based on the image data, the
printed circuit board must be reliably fixed when being imaged.
Therefore, an AVI device is provided with an inspection platform
including a holding mechanism that holds the printed circuit board.
Examples of the holding mechanism include a clamp mechanism, a vacuum
suction mechanism and an electrostatic adsorption mechanism.

[0008] In an inspection platform including the clamp mechanism
(hereinafter referred to as a clamp inspection platform), ends of the
printed circuit board are fixed on the inspection platform by a plurality
of clamps while the printed circuit board is placed on the inspection
platform.

[0009] An inspection platform including the vacuum suction mechanism
(hereinafter referred to as a vacuum inspection platform) has a through
hole that penetrates the inspection platform from its upper surface to
its lower surface, for example. In addition, a suction device that sucks
in an atmosphere above the upper surface of the inspection platform
through the through hole is provided on a lower surface side of the
inspection platform. The suction device is operated while the printed
circuit board is placed on the inspection platform, so that the printed
circuit board is attracted through the through hole by the suction device
to be fixed on the inspection platform.

[0010] An inspection platform including the electrostatic adsorption
mechanism (hereinafter referred to as an electrostatic inspection
platform) includes an insulator that forms an upper surface of the
inspection platform, for example. An electrical conductor is provided
below the insulator. The electrical conductor is composed of a positive
electrode plate and a negative electrode plate each arranged in parallel
with the upper surface of the inspection platform. Voltage is applied
between the positive electrode plate and the negative electrode plate of
the electrical conductor while the printed circuit board is placed on the
inspection platform, so that the insulator polarizes to induce positive
charges and negative charges on the upper surface of the inspection
platform. Thus, an electrostatic force (Coulomb force) arising from the
induced positive charges and negative charges causes the printed circuit
board to be adsorbed on the upper surface of the inspection platform to
be fixed on the inspection platform.

[0011] Since the ends of the printed circuit board are fixed by the
plurality of clamps in the above-described clamp inspection platform, a
tensile force is exerted between the plurality of ends of the printed
circuit board. Therefore, the printed circuit board may be fixed on the
inspection platform while having wrinkles generated thereon. In this
case, it is difficult to perform accurate AVI.

[0012] If a number of holes are formed in the printed circuit board, the
printed circuit board cannot be adsorbed on the inspection platform in
some cases in the vacuum inspection platform. In addition, a suction
force is locally generated in the portion where the through hole is
formed in the inspection platform. Therefore, an uneven suction force is
exerted on the printed circuit board, thereby causing strain in the
printed circuit board in some cases. Also in this case, it is difficult
to perform accurate AVI.

[0013] In the electrostatic inspection platform, since the object is
adsorbed by the electrostatic force, a sufficient adsorption force cannot
be obtained in a case where the printed circuit board and the upper
surface of the inspection platform are not in close proximity to each
other. Therefore, the printed circuit board cannot be adsorbed on the
upper surface of the inspection platform when strain such as warp occurs
in the printed circuit board. In this case, it is difficult to perform
accurate AVI.

[0014] JP 2002-76569 A describes an inspection device of a printed board
using the electrostatic inspection platform. In the inspection device,
the printed board is pressed against the upper surface of the inspection
platform by a squeeze roller while being electrostatically adsorbed on
the inspection platform. This causes the printed board to be flattened on
the inspection platform.

[0015] In fact, however, a frictional force or the like occurs between the
printed board and the squeeze roller, causing wrinkles in the printed
board in some cases. In addition, the surface of the squeeze roller is
adhesive. Therefore, when the printed board happens to stick to the
squeeze roller, it may be raised from the inspection platform as the
squeeze roller moves. Also in these cases, it is difficult to perform
accurate AVI.

BRIEF SUMMARY OF THE INVENTION

[0016] An object of the present invention is to provide a method of
inspecting a printed circuit board, a method of manufacturing a printed
circuit board and an inspection device of a printed circuit board that
allow for accurate automatic appearance inspection.

[0017] (1) According to an aspect of the present invention, a method of
inspecting a printed circuit board includes the steps of placing the
printed circuit board on a support surface of an adsorption platform,
placing a pressing member on the printed circuit board placed on the
support surface such that the printed circuit board is pressed by an
insulating pressing surface of the pressing member, adsorbing the printed
circuit board on the support surface by an electrostatic force by
charging the support surface while the printed circuit board and the
pressing member are placed on the support surface, removing the pressing
member placed on the printed circuit board while the support surface is
charged, and performing automatic appearance inspection on the printed
circuit board adsorbed on the support surface.

[0018] In the inspecting method, the printed circuit board is placed on
the support surface of the adsorption platform, and the pressing member
is placed on the printed circuit board placed on the support surface such
that the printed circuit board is pressed by the insulating pressing
surface of the pressing member. Thus, the entire surface of the printed
circuit board is uniformly pressed by the pressing member, so that the
printed circuit board uniformly comes in contact with the support surface
of the adsorption platform while being flattened.

[0019] The support surface of the adsorption platform is charged in this
state, thereby causing the printed circuit board to be adsorbed on the
support surface by an electrostatic force. This causes the printed
circuit board to be fixed in a flattened state on the support surface.

[0020] Then, the pressing member placed on the printed circuit board is
removed while the support surface is charged, and the automatic
appearance inspection is performed on the printed circuit board adsorbed
on the support surface. Accordingly, the automatic appearance inspection
can be accurately performed while the flattened printed circuit board is
reliably fixed on the support surface of the adsorption platform.

[0021] (2) The pressing surface of the pressing member may be formed of
insulating glass or insulating resin. The pressing surface of the
pressing member is formed of the insulating material, thereby reliably
preventing discharge from being generated between the support surface and
the pressing member.

[0022] The insulating glass or the insulating resin easily becomes
charged. Therefore, if the support surface is charged with the printed
circuit board and the pressing member placed thereon, the pressing member
also becomes charged in some cases. In this case, the pressing surface of
the pressing member becomes charged, so that foreign matters on the
printed circuit board are adsorbed on the pressing surface of the
pressing member by an electrostatic force. Accordingly, the foreign
matters on the printed circuit board are adsorbed on the pressing surface
to be removed from the printed circuit board when the pressing member is
removed from the support surface.

[0023] (3) The resin may include at least one of polyvinyl chloride,
acrylic resin, polycarbonate and polytetrafluoroethylene.

[0024] Polyvinyl chloride, acrylic resin, polycarbonate and
polytetrafluoroethylene are insulating materials that are easily charged.
Thus, discharge can be reliably prevented from being generated between
the support surface of the adsorption platform and the pressing surface
of the pressing member, and foreign matters on the printed circuit board
can be reliably removed.

[0025] (4) The pressing member may be formed of a material having light
transmission properties.

[0026] In this case, the printed circuit board can be seen through the
pressing member when the pressing member is placed on the printed circuit
board placed on the support surface, thus allowing for confirmation as to
whether or not the printed circuit board is accurately positioned on the
support surface.

[0027] (5) According to another aspect of the present invention, a method
of manufacturing a printed circuit board includes the steps of preparing
the printed circuit board before inspection by forming a conductor trace
on an insulating layer, placing the printed circuit board before
inspection on a support surface of an adsorption platform, placing a
pressing member on the printed circuit board before inspection placed on
the support surface such that the printed circuit board before inspection
is pressed by an insulating pressing surface of the pressing member,
adsorbing the printed circuit board before inspection on the support
surface by an electrostatic force by charging the support surface while
the printed circuit board before inspection and the pressing member are
placed on the support surface, removing the pressing member placed on the
printed circuit board before inspection while the support surface is
charged, and performing automatic appearance inspection on the printed
circuit board before inspection adsorbed on the support surface.

[0028] In the manufacturing method, the printed circuit board before
inspection is prepared by forming the conductor trace on the insulating
layer, and the prepared printed circuit board before inspection is placed
on the support surface of the adsorption platform. The pressing member is
placed on the printed circuit board before inspection placed on the
support surface such that the printed circuit board before inspection is
pressed by the insulating pressing surface of the pressing member. Thus,
the entire surface of the printed circuit board before inspection is
uniformly pressed by the pressing member, so that the printed circuit
board before inspection uniformly comes in contact with the support
surface of the adsorption platform while being flattened.

[0029] The support surface of the adsorption platform becomes charged in
this state, thereby causing the printed circuit board before inspection
to be adsorbed on the support surface by an electrostatic force. This
causes the printed circuit board before inspection to be fixed in a
flattened state on the support surface.

[0030] Then, the pressing member placed on the printed circuit board
before inspection is removed while the support surface is charged, and
the automatic appearance inspection is performed on the printed circuit
board adsorbed on the support surface. Accordingly, the automatic
appearance inspection can be accurately performed while the flattened
printed circuit board before inspection is reliably fixed on the support
surface of the adsorption platform. This allows for accurate
determination as to whether or not the printed circuit board is
defective.

[0031] (6) According to still another aspect of the present invention, an
inspection device of a printed circuit board includes an adsorption
platform that has a support surface on which the printed circuit board is
placed, and is configured such that the support surface can be switched
between a charged state and an uncharged state, a pressing member that
has an insulating pressing surface, a moving device arranged to move the
pressing member, a detection device arranged to perform automatic
appearance inspection on the printed circuit board placed on the support
surface of the adsorption platform, and a controller arranged to control
operations of the adsorption platform, the moving device and the
detection device, wherein the controller controls the moving device to
place the pressing member on the printed circuit board such that the
printed circuit board is pressed by the pressing surface while the
printed circuit board is placed on the support surface of the adsorption
platform, switches the support surface of the adsorption platform to the
charged state while the printed circuit board and the pressing member are
placed on the support surface to cause the printed circuit board to be
adsorbed on the support surface by an electrostatic force, controls the
moving device to remove the pressing member placed on the printed circuit
board in the charged state of the support surface, and controls the
detection device to perform automatic appearance inspection on the
printed circuit board adsorbed on the support surface.

[0032] With the printed circuit board placed on the support surface of the
adsorption platform, the pressing member is placed on the printed circuit
board placed on the support surface by the moving device such that the
printed circuit board is pressed by the insulating pressing surface of
the pressing member in the inspection device. Thus, the entire surface of
the printed circuit board is uniformly pressed by the pressing member, so
that the printed circuit board uniformly comes in contact with the
support surface of the adsorption platform while being flattened.

[0033] In this state, the support surface of the adsorption platform is
switched to the charged state, thereby causing the printed circuit board
to be adsorbed on the support surface by an electrostatic force. This
causes the printed circuit board to be fixed in a flattened state on the
support surface.

[0034] Then, the pressing member placed on the printed circuit board is
removed by the moving device while the support surface is charged, and
the detecting device performs the automatic appearance inspection on the
printed circuit board adsorbed on the support surface. Accordingly,
accurate automatic appearance inspection can be performed while the
flattened printed circuit board is reliably fixed on the support surface
of the adsorption platform.

[0035] Other features, elements, characteristics, and advantages of the
present invention will become more apparent from the following
description of preferred embodiments of the present invention with
reference to the attached drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0036] FIG. 1 is a plan view of a suspension board.

[0037] FIG. 2 (a) is a sectional view of the suspension board of FIG. 1
taken along the line A-A.

[0038] FIG. 2 (b) is a sectional view of the suspension board of FIG. 1
taken along the line B-B.

[0040] FIG. 4 is a partially enlarged plan view showing an assembly sheet
after a cutting out step.

[0041] FIG. 5 is a block diagram showing one example of the configuration
of an AVI device used in a final inspecting step of FIG. 3.

[0042] FIG. 6 is a diagram for explaining an operation of the AVI device
at the time of AVI in the final inspecting step of FIG. 3.

[0043] FIG. 7 is a plan view of a substrate adsorption platform on which a
pressing plate of FIG. 5 is placed.

[0044] FIG. 8 is a diagram for explaining how foreign matters are removed
from assembly sheets by the pressing plate of FIG. 5.

[0045] FIG. 9 is a block diagram showing another example of the
configuration of the substrate adsorption platform.

DETAILED DESCRIPTION OF THE INVENTION

[0046] Hereinafter, description will be made of a method of inspecting a
printed circuit board, a method of manufacturing a printed circuit board
and an inspection device of a printed circuit board according to an
embodiment of the present invention while referring to the drawings. The
method of inspecting the printed circuit board and the inspection device
of the printed circuit board according to the present embodiment are used
in an automatic appearance inspecting step for determining whether or not
a suspension board with circuits (hereinafter abbreviated as a suspension
board) is defective in manufacture of the suspension board described
below, for example. The automatic appearance inspection includes AVI
(Automatic Visual Inspection) and AOI (Automatic Optical Inspection), for
example. First, description is made of the configuration of the
suspension board to be inspected.

[0047] (1) Configuration of the Suspension Board

[0048] FIG. 1 is a plan view of the suspension board. FIG. 2 (a) and (b)
are sectional views of the suspension board of FIG. 1 taken along the
line A-A and the line B-B, respectively.

[0049] As shown in FIG. 1, the suspension board 1 includes a suspension
body 20 formed of a support substrate 10 (see FIG. 2), described below,
and an insulating layer 11. Conductor traces 25 are formed on the
suspension body 20. The conductor traces 25 are schematically indicated
by hatching in FIG. 1. At the tip of the suspension body 20, a U-shaped
opening 26 is formed, thereby providing a magnetic head supporting
portion (hereinafter referred to as a tongue) 24. The tongue 24 is bent
along the broken line R to form a given angle with respect to the
suspension body 20.

[0050] Four electrode pads 22 are formed at an end of the tongue 24. Four
electrode pads 27 are formed at the other tip of the suspension body 20.
The electrode pads 22 on the tongue 24 and the electrode pads 27 at the
other tip of the suspension body 20 are electrically connected to one
another through the conductor traces 25. A plurality of holes 28 are
formed in the suspension body 20. A cover layer 18 (see FIG. 2),
described below, is not shown in FIG. 1.

[0051] As shown in FIG. 2 (a), the insulating layer 11 made of polyimide
is formed on the support substrate 10 made of stainless steel in the
cross section taken along the line A-A of FIG. 1. A chromium film 12 and
a conductor layer 16 that is made of copper are sequentially stacked at
four positions on the insulating layer 11, and an electrode pad 27 made
of gold is formed on each of the conductor layers 16. An upper surface of
the insulating layer 11 is covered with the cover layer 18 made of
polyimide with upper surfaces of the electrode pads 27 uncovered.

[0052] As shown in FIG. 2 (b), the insulating layer 11 made of polyimide
is formed on the support substrate 10 made of stainless steel also in the
cross section taken along the line B-B of FIG. 1. The chromium film 12
and the conductor layer 16 that is made of copper are sequentially
stacked at respective two positions on one side portion and the other
side portion of the insulating layer 11. The two sets of chromium film 12
and conductor layer 16 on each side portion are covered with the cover
layer 18 made of polyimide. Traces each composed of the chromium film 12
and the conductor layer 16 constitute the conductor traces 25.

[0053] (2) Manufacture of the Suspension Board

[0054] The foregoing suspension board 1 is prepared as follows, for
example. In the manufacturing processes of the suspension board 1, an
assembly sheet on which the plurality of suspension boards 1 are
integrally formed is prepared as a half-finished product. Details of the
assembly sheet will be described below. FIG. 3 is a schematic flowchart
showing steps of manufacturing the suspension board 1 of FIG. 1.

[0055] First, a long-sized support substrate 10 is prepared as mentioned
in FIG. 3 (a support substrate preparing step: Step S1). A stainless
steel plate, for example, can be used as the support substrate 10. Here,
a plurality of regions of the support substrate 10 corresponding to the
plurality of suspension boards 1 are referred to as substrate regions.

[0056] Next, the insulating layer 11 is integrally formed on one surface
of the prepared support substrate 10 (an insulating layer forming step:
Step S2). The conductor traces 25 each composed of the chromium film 12
and the conductor layer 16 are formed on the insulating layer 11 (a
conductor trace forming step: Step S3). Here, the plurality of conductor
traces 25 of FIG. 1 are formed on each of the plurality of substrate
regions of the support substrate 10. The conductor traces 25 may be
formed using an additive method or a semi-additive method, for example.
Alternatively, another method such as a subtractive method may be used.

[0057] Then, the cover layer 18 (see FIG. 2) made of polyimide having a
given pattern is formed on the insulating layer 11 and the conductor
traces 25 (a cover layer forming step: Step S4).

[0058] With the cover layer 18 formed, the four electrode pads 22 and the
four electrode pads 27 are formed on the positions of the conductor
traces 25 corresponding to the tongue 24 and the other tip of the
suspension body 20 of FIG. 1, respectively (an electrode forming step:
Step S5).

[0059] Next, continuity check, AOI and visual check are sequentially
performed in order to detect defects in the conductor traces 25 formed in
the plurality of substrate regions (a conductor trace inspecting step:
Step S6).

[0060] In the continuity check, electrical continuity of the conductor
traces 25 formed on each substrate region is inspected. In the AOI, image
data obtained by imaging good conductor traces 25 with no defect is
compared with image data obtained by imaging the conductor traces 25 to
be inspected, thereby detecting defects in the conductor traces 25 to be
inspected. After the continuity check and the AOI, a worker visually
checks using a microscope positions in which defects are detected through
the AOI. Accordingly, defects in the conductor traces 25 are reliably
detected.

[0061] Then, given regions of the support substrate 10 excluding the
plurality of substrate regions are cut out (a cutting out step: Step S7).
In this manner, the assembly sheet in which the plurality of suspension
boards 1 are integrally formed is completed.

[0062] FIG. 4 is a partially enlarged plan view showing the assembly sheet
after the cutting out step. As shown in FIG. 4, the plurality of
suspension boards 1 are arranged along one direction within a
substantially rectangular frame CF in the assembly sheet 100. Coupling
portions JP that couple the frame CF and each suspension board 1 are
formed inside the frame CF.

[0063] Returning to FIG. 3, finally, the AVI is performed for determining
whether or not each suspension board 1 of the assembly sheet 100 is
defective (a final inspecting step: Step S8). In the AVI, determination
as to whether or not the plurality of suspension boards 1 prepared
through the foregoing Steps S1 to S7 have defects in the conductor
traces, dimensional errors of the conductor traces, defects in terminals,
damages on resist surfaces and so on is made in a short period of time.
Details will be described below.

[0064] The suspension boards 1 that are not determined to be defective in
the AVI are removed from the frame CF by cutting off the coupling
portions JP and shipped as acceptable products (good products).

[0065] (3) Configuration of AVI Device

[0066] The AVI in the final inspecting step of FIG. 3 is performed using
an AVI device described below. FIG. 5 is a block diagram showing one
example of the configuration of the AVI device used in the final
inspecting step of FIG. 3.

[0068] The substrate adsorption platform 20A is a bipolar electrostatic
adsorption platform that adsorbs an object (the assembly sheet 100 in
this example) by an electrostatic force. The substrate adsorption
platform 20A includes an insulator 21, a positive plate 22a, a negative
plate 22b and a DC power supply device 23.

[0069] The insulator 21 is formed of an insulating material such as
ceramic, and forms an upper surface of the substrate adsorption platform
20A, that is, a surface on which the assembly sheets 100 are placed. In
the present embodiment, the upper surface of the substrate adsorption
platform 20A is formed such that its length and width measurement are
each 350 mm, for example. Surface roughness, which is surface roughness
(Ra) based on JIS (Japanese Industrial Standards) B 0601, of the
insulator 21 is preferably not more than 10 μm, for example, in the
upper surface of the substrate adsorption platform 20A.

[0070] The positive plate 22a and the negative plate 22b are each formed
of an electrically conductive material such as copper, for example, and
are arranged adjacent to each other in positions spaced apart from the
upper surface of the insulator 21 inside the insulator 21. The positive
plate 22a is connected to a positive terminal of the DC power supply
device 23. The negative plate 22b is connected to a negative terminal of
the DC power supply device 23.

[0071] When the DC power supply device 23 is turned on, a voltage is
applied between the positive plate 22a and the negative plate 22b. This
causes the insulator 21 to polarize, resulting in induction of positive
charges and negative charges in the upper surface of the substrate
adsorption platform 20A, as will be described below. Accordingly, an
electrostatic force arising from the induced positive charges and
negative charges works as an adsorption force between the substrate
adsorption platform 20A, described below, and the assembly sheets 100. On
the other hand, a voltage is not applied between the positive plate 22a
and the negative plate 22b when the DC power supply device 23 is turned
off. Thus, the electrostatic force is not generated in the upper surface
of the substrate adsorption platform 20A. Details of an operation of the
substrate adsorption platform 20A will be described below.

[0072] As indicated by the one-dot and dash line in FIG. 5, the pressing
plate moving device 32 supports the pressing plate 31 in a movable manner
between a position above the substrate adsorption platform 20A and a
position beside the substrate adsorption platform 20A.

[0073] The pressing plate 31 is formed of an insulating material. A
material that is easily charged is preferably used as the insulating
material for the pressing plate 31. In this case, glass or resin such as
polyvinyl chloride, acrylic resin, polycarbonate or
polytetrafluoroethylene, for example, can be used as the pressing plate
31.

[0074] In the present embodiment, the pressing plate 31 is formed such
that its length and width measurements are each 350 mm and its thickness
is 10 mm, for example, similarly to the upper surface of the substrate
adsorption platform 20A. The pressing plate 31 preferably has weight of
10 kg/m2 or more.

[0075] The CCD camera 41 is provided above the substrate adsorption
platform 20A. The CCD camera 41 is supported by the camera moving device
42 in a horizontally movable manner in a region above the upper surface
of the substrate adsorption platform 20A.

[0076] The CCD camera 41 is provided with the light source 43. The image
processing device 44 and the memory 45 are connected to the CCD camera
41.

[0077] The controller 50 of the AVI device 200 is composed of a CPU
(Central Processing Unit) and a memory or composed of a microcomputer,
for example, and controls operations of components of the AVI device 200.

[0078] (4) Operation of the AVI Device

[0079] FIG. 6 is a diagram for explaining an operation of the AVI device
at the time of the AVI in the final inspecting step of FIG. 3. FIG. 6 (a)
to (d) show schematic side views of the substrate adsorption platform 20A
in the AVI device 200.

[0080] As shown in FIG. 6 (a), the plurality of assembly sheets 100 are
placed on the substrate adsorption platform 20A such that the surfaces of
the conductor traces 25 face the CCD camera 41. In this case, the
plurality of assembly sheets 100 to be inspected are placed on the
substrate adsorption platform 20A while being manually positioned by a
worker, for example. The plurality of assembly sheets 100 may be placed
on the substrate adsorption platform 20A by a transport device for the
assembly sheets 100.

[0081] Next, the controller 50 controls the pressing plate moving device
32 to place the pressing plate 31 on the upper surface of the substrate
adsorption platform 20A as shown in FIG. 6 (b). At this time, the DC
power supply device 23 of the substrate adsorption platform 20A is
maintained in an OFF state.

[0082] FIG. 7 is a plan view of the substrate adsorption platform 20A on
which the pressing plate 31 of FIG. 5 is placed. In the example of FIG.
7, the pressing plate 31 is placed on the upper surface of the substrate
adsorption platform 20A to cover the entire four assembly sheets 100
while the assembly sheets 100 are placed on the upper surface of the
substrate adsorption platform 20A.

[0083] This causes the plurality of assembly sheets 100 on the substrate
adsorption platform 20A to be pressed against the upper surface of the
substrate adsorption platform 20A by the pressing plate 31. As a result,
a uniform pressing force is exerted on the entire surfaces of the
plurality of assembly sheets 100 (see the arrows in FIG. 6 (b)).

[0084] At this time, since the DC power supply device 23 is turned off, an
adsorption force arising from the electrostatic force is not generated in
the upper surface of the substrate adsorption platform 20A. Therefore,
each assembly sheet 100 is easily flattened on the upper surface of the
substrate adsorption platform 20A by the pressing force of the pressing
palate 31.

[0085] Here, a material having high light transmission properties (light
transmittance is 80% or more in a wavelength region including at least
part of a wavelength region of visible light, for example) is preferably
used as the pressing plate 31. This allows for confirmation as to whether
or not the assembly sheets 100 are accurately positioned on the substrate
adsorption platform 20A when being pressed.

[0086] Then, the DC power supply device 23 is switched from the OFF state
to an ON state by the controller 50 as shown in FIG. 6 (c). At this time,
an electric field is generated between the positive plate 22a and the
negative plate 22b to cause the insulator 21 covering the upper surfaces
of the positive plate 22a and the negative plate 22b to polarize.

[0087] In this case, positive charges are induced in a portion of the
upper surface of the insulator 21 above the positive plate 22a, and
negative charges are induced in a portion of the upper surface of the
insulator 21 above the negative plate 22b. This causes an electrostatic
force (Coulomb force) arising from the induced positive charges and
negative charges to be generated between the upper surface of the
substrate adsorption platform 20A and the conductor portions (the support
substrates 10 and the conductor traces 25 each formed of the electrically
conductive materials, for example) of the assembly sheets 100. The
generated electrostatic force works as an adsorption force between the
substrate adsorption platform 20A and the assembly sheets 100. As a
result, the plurality of assembly sheets 100 are held by adsorption on
the upper surface of the substrate adsorption platform 20A while being
flattened.

[0088] After that, with the DC power supply device 23 maintained in the ON
state, the controller 50 controls the pressing plate moving device 32 to
outwardly move the pressing plate 31 from the position above the upper
surface of the substrate adsorption platform 20A as shown in FIG. 6 (d).

[0089] Thus, the upper surfaces of the assembly sheets 100 are exposed
while the plurality of flattened assembly sheets 100 are held by
adsorption on the upper surface of the substrate adsorption platform 20A.

[0090] In this state, the controller 50 controls the camera moving device
42 to move the CCD camera 41 above the substrate adsorption platform 20A.
At this time, the light source 43 emits light to cause the plurality of
suspension boards 1 of the plurality of assembly sheets 100 to be
irradiated with light having a given wavelength. Then, reflected light
from each suspension board 1 is imaged by the CCD camera 41.

[0092] Before the AVI is started, a good suspension board 1 with no defect
is previously imaged by the CCD camera 41, obtained image data is
processed based on the predetermined image processing conditions, and the
processed image data is stored in the memory 45 as master data.

[0093] In the AVI, the controller 50 compares the inspection target data
with the master data stored in the memory 45, and determines the
presence/absence of defects in each suspension board 1.

[0094] Finally, all the suspension boards 1 on the substrate adsorption
platform 20A are imaged, so that the DC power supply device 23 is
switched from the ON state to the OFF state. This removes the adsorption
force between the substrate adsorption platform 20A and the assembly
sheets 100, and the assembly sheets are recovered.

[0095] As described above, the pressing plate 31 is formed of the
insulating material. The reason is described below.

[0096] In the AVI, the assembly sheets 100 and the pressing plate 31 are
placed on the substrate adsorption platform 20A, and the pressing plate
31 is removed while the DC power supply device 23 is maintained in the ON
state. At this time, electric discharge may be induced between the
pressing plate 31 and the upper surface of the substrate adsorption
platform 20A if the pressing plate 31 is formed of an electrically
conductive material. This causes the suspension boards 1 on the substrate
adsorption platform 20A to be damaged in some cases. Therefore, the
pressing plate 31 is formed of the insulating material in the present
embodiment.

[0097] (5) Effects

[0098] (a) In the present embodiment, the plurality of assembly sheets 100
are placed on the upper surface of the substrate adsorption platform 20A,
and the pressing plate 31 is placed on the plurality of assembly sheets
100 placed on the substrate adsorption platform 20A such that the
plurality of assembly sheets 100 are pressed by the pressing plate 31.
Since the entire surfaces of the plurality of assembly sheets 100 are
uniformly pressed by the pressing plate 31, the plurality of assembly
sheets 100 uniformly come in contact with the upper surface of the
substrate adsorption platform 20A while being flattened.

[0099] In this state, the DC power supply device 23 enters the ON state
and the upper surface of the substrate adsorption platform 20A is
charged, so that the plurality of assembly sheets 100 are adsorbed on the
upper surface of the substrate adsorption platform 20A by the
electrostatic force. Accordingly, the plurality of assembly sheets 100
are fixed on the upper surface of the substrate adsorption platform 20A
while being flattened.

[0100] Then, the pressing plate 31 placed on the plurality of assembly
sheets 100 is removed while the upper surface of the substrate adsorption
platform 20A is charged, and the AVI is performed on the plurality of
assembly sheets 100 adsorbed on the upper surface of the substrate
adsorption platform 20A. This allows for the accurate AVI while the
plurality of flattened assembly sheets 100 are reliably fixed on the
upper surface of the substrate adsorption platform 20A.

[0101] While the pressing plate 31 is placed on the substrate adsorption
platform 20A and removed from the substrate adsorption platform 20A by
the pressing plate moving device 32 of FIG. 5 in the present embodiment,
these operations may be manually performed by a worker.

[0102] (b) In the present embodiment, the pressing plate 31 is removed
from the upper surface of the substrate adsorption platform 20A while the
DC power supply device 23 is maintained in the ON state as described
above. In this case, foreign matters such as particles can be removed
from the upper surface of the assembly sheet 100 that is adsorbed on the
substrate adsorption platform 20A. Details are described below.

[0103] FIG. 8 is a diagram for explaining how foreign matters are removed
from the assembly sheets 100 by the pressing plate 31 of FIG. 5. FIG. 8
(a), (b) each show a schematic side view of the substrate adsorption
platform 20A in the AVI device 200.

[0104] In the present embodiment, the insulating material that is easily
charged is used as the pressing plate 31. As shown in FIG. 8 (a), when
the DC power supply device 23 enters the ON state while the plurality of
assembly sheets 100 and the pressing plate 31 are placed on the upper
surface of the substrate adsorption platform 20A, the positive charges
are induced in the portion of the upper surface of the insulator 21 above
the positive plate 22a and the negative charges are induced in the
portion of the upper surface of the insulator 21 above the negative plate
22b as described above.

[0105] This generates electrostatic induction in the conductor portions of
the plurality of assembly sheets 100. In the example of FIG. 8, positive
charges are induced on an upper surface side of the assembly sheet 100
positioned above the positive plate 22a, and negative charges are induced
on an upper surface side of the assembly sheet 100 positioned above the
negative plate 22b.

[0106] This causes the pressing plate 31 covering the plurality of
assembly sheets 100 to polarize. Specifically, negative charges are
induced on a lower surface side of a portion of the pressing plate 31
positioned above the positive plate 22a, and positive charges are induced
on a lower surface side of a portion of the pressing plate 31 positioned
above the negative plate 22b.

[0107] Therefore, when foreign matters P exist on the upper surfaces of
the assembly sheets 100, that is, between the assembly sheets 100 and the
pressing plate 31, an electrostatic force that adsorbs the foreign
matters P to a lower surface of the pressing plate 31 is generated.

[0108] As a result, when the pressing plate 31 is removed, the foreign
matters P on the assembly sheets 100 are adsorbed to the lower surface of
the pressing plate 31 to be removed from the upper surfaces of the
assembly sheets 100 as shown in FIG. 8 (b).

[0109] (6) Another Example of the Configuration of the Substrate
Adsorption Platform

[0110] A unipolar electrostatic adsorption platform including any of the
positive plate 22a and the negative plate 22b inside the insulator 21 may
be used instead of the bipolar substrate adsorption platform 20A of FIGS.
5 to 8.

[0111] FIG. 9 is a block diagram showing another example of the
configuration of the substrate adsorption platform 20A. The substrate
adsorption platform 20A of this example includes the insulator 21, the
positive plate 22a and the DC power supply device 23. These components
are the same as those in the substrate adsorption platform 20A of FIG. 5.

[0112] In the substrate adsorption platform 20A, the positive plate 22a is
connected to the positive terminal of the DC power supply device 23.
Then, each assembly sheet 100 on the substrate adsorption platform 20A is
connected to the negative terminal of the DC power supply device 23.

[0113] When the DC power supply device 23 is turned on, a voltage is
applied between the positive plate 22a and the plurality of assembly
sheets 100. This causes the insulator 21 to polarize, resulting in
induction of positive charges and negative charges in the upper surface
of the substrate adsorption platform 20A. Accordingly, an electrostatic
force arising from the induced positive charges and negative charges
works as an adsorption force between the substrate adsorption platform
20A and the assembly sheets 100. On the other hand, when the DC power
supply device 23 is turned off, a voltage is not applied between the
positive plate 22a and the plurality of assembly sheets 100. Thus, the
electrostatic force is not generated in the upper surface of the
substrate adsorption platform 20A.

[0114] In this manner, the electrostatic force can be easily generated at
desired timings in the substrate adsorption platform 20A by switching the
DC power supply device 23 between the ON state and the OFF state in the
unipolar electrostatic adsorption platform 20A of FIG. 9, similarly to
the bipolar substrate adsorption platform 20A of FIGS. 5 to 8.

[0115] Accordingly, in the final inspecting step, the substrate adsorption
platform 20A of this example provides the same effects as those described
above.

[0116] (7) Modifications

[0117] While the plate-shaped pressing plate 31 is used for pressing the
plurality of assembly sheets 100 against the upper surface of the
substrate adsorption platform 20A in the present embodiment, the present
invention is not limited to this.

[0118] A configuration for pressing the plurality of assembly sheets 100
against the upper surface of the substrate adsorption platform 20A can be
achieved by having an insulating pressing surface that presses the
plurality of assembly sheets 100 against the upper surface of the
substrate adsorption platform 20A. Therefore, a projection such as a pull
may be formed on a surface on the opposite side of the pressing surface
of the pressing plate 31, for example. Also in this case, the same
effects as described above can be obtained.

[0119] (8) Correspondences Between Elements in the Claims and Parts in
Embodiments

[0120] In the following paragraphs, non-limiting examples of
correspondences between various elements recited in the claims below and
those described above with respect to various preferred embodiments of
the present invention are explained.

[0121] In the foregoing embodiment, the assembly sheet 100 and the
suspension board 1 are examples of a printed circuit board, the substrate
adsorption platform 20A is an example of an adsorption platform, and the
upper surface of the substrate adsorption platform 20A is an example of a
support surface.

[0122] The pressing plate 31 is an example of a pressing member, the lower
surface of the pressing plate 31 is an example of a pressing surface, and
the pressing plate moving device 32 is an example of a moving device.

[0123] The CCD camera 41, the camera moving device 42, the image
processing device 44, the memory 45 and the controller 50 are an example
of a detection device.

[0124] As each of various elements recited in the claims, various other
elements having configurations or functions described in the claims can
be also used.

[0125] While preferred embodiments of the present invention have been
described above, it is to be understood that variations and modifications
will be apparent to those skilled in the art without departing the scope
and spirit of the present invention. The scope of the present invention,
therefore, is to be determined solely by the following claims.